1. Field of the Invention
The invention pertains to transaxle drive units consisting of transmission gearing and wheel drive shafts enclosed within removable casing components.
2. Description of the Related Art
Transaxle transmissions are often utilized with small utility vehicles such as riding lawnmowers, small garden tractors, and the like. Such vehicles combine the transmission gearing with the wheel drive shafts and associated differential wherein the transmission gearing as well as the wheel drive shaft differential gearing are located within a common housing. Such a combination of a transmission, differential and drive wheel shaft are commonly called "transaxles" and are widely used with small vehicles due to economy of manufacture and assembly.
Typical transaxle constructions and utilization are shown in U.S. Pat. Nos. 3,311,186; 4,662,241 and 4,673,055.
As transaxles are commonly used with small utility vehicles, it is necessary to incorporate wheel brake structure with the vehicle drive mechanism, and with transaxles, such brakes usually include a disc or drum shaft extending from the transaxle housing and rotated by the transmission gearing, and a brake shoe or disc selectively frictionally engages with the drum or disc to brake the rotation of the associated transmission gearing, and vehicle. Such commonly utilized transaxle braking systems are mounted exteriorly of the transmission housing, and have the disadvantage of being located in the transmission path outside of the interconnection of the wheel drive shafts and the differential. Accordingly, even though the brake structure may be fully applied and "locked up", it is possible for the vehicle wheels to rotate in opposite directions through the interconnecting differential, as may happen on slopes, particularly when the grass or terrain is wet or slippery. Such failure of the brake to adequately control vehicle movement raises serious safety ramifications as under such conditions the vehicle brake becomes inoperative with respect to stopping vehicle movement.
In previously known transaxle constructions, such as typified in the above mentioned patents, transaxles utilizing differentially connected wheel drive shafts only permit safe braking if the drive shaft tires are upon a dry surface which is often not the case with riding lawnmowers and small tractors.
Transaxle housings are usually defined by two casings bolted together along a flat assembly surface, and as the bolt-together casing parts are relatively large, the internal transaxle components may be easily assembled within the housing. Particularly, ease of assembly is experienced when the assembly surface plane constitutes a diameter of the wheel drive shafts whereby the drive shafts may be "dropped into" the lower casing with minimal assembly time required. However, previously, brake structure has not been available for transaxle units capable of truly braking the vehicle drive wheels under all conditions and situations, or wherein the brake structure is incorporated within the transaxle housing and casing configuration.